Liquid crystal display and method for driving same

ABSTRACT

Disclosed is an LCD comprising a plurality of data lines extending in a first direction, a plurality of gate lines extending in a second direction defining with the plurality of data lines a plurality of pixel areas arranged in a matrix configuration and supplying a gate signal to at least two rows of the pixel areas simultaneously. Thin film transistors are connected to the plurality of gate lines and the plurality of data lines. Also disclosed is a driving method for an LCD including a thin film transistor substrate including pixel areas arranged in a matrix form with a gate line extending in a first direction and a data line extending in a second direction, along with a backlight providing the TFT substrate with light of three primary colors. In the method, the three primary colors are sequentially provided in one frame period and at least two rows of pixel areas and simultaneously provided with a common gate signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/366,867, filed Mar. 1, 2006, which claims the benefit of KoreanPatent Application No. 2005-0017228, filed on Mar. 2, 2005, in theKorean Intellectual Property Office, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD) and adriving method of the same, and more particularly, to an LCD having animproved gate signal application and an improved gate signal applicationmethod.

2. Description of the Related Art

Recently, there has been a desire for a lightweight and thin displayapparatus. Such desire has caused CRTs (cathode ray tube) to be replacedwith flat display apparatuses like an LCD.

Typically an LCD display apparatus is comprised of two substrates and aliquid crystal layer having a dielectric anisotropy disposedtherebetween. The LCD applies an electric field to the liquid crystallayer and controls the intensity of the electric field, therebydisplaying an image, wherein the transmittance of light passing throughthe substrate is adjusted according to the intensity of the electricfield.

Generally, the conventional LCD has a color filter layer composed ofthree primary colors i.e. red (R), green (G) and blue (B), and controlsthe transmittance of light passing through the color filter layer,thereby displaying a required color.

Such an LCD needs pixels corresponding to each R, G and B regions.Therefore, the LCD needs three times more pixels than when it displays ablack and white image. Accordingly, the liquid crystal panel of the LCDhas to be fabricated with precision so that a high resolution image canbe displayed.

Further, fabricating the additional color filter layer on the substrateis intricate, and the transmittance of light for the color filter layerneeds to be improved.

Due to the above problems, there has been created an LCD using a FSC(field sequential color) method. The FSC method lights independent R, Gand B light sources sequentially and periodically, and transmits a colorsignal corresponding to each pixel with a synchronization with thelighting period, thereby producing a full color image.

In this FSC method, the three light sources are sequentially lighted toform one frame. Therefore, the FSC method needs to have a frequencythree times higher than the conventional driving method. With the FSCmethod, the term frequency means how many times the frames are refreshedin one second. As the display apparatuses become large, the number ofgate lines increases, yet a gate on time decreases. The gate on timerepresents how long gate on voltage is applied to one gate line.Therefore, the gate on time is the reciprocal of the product of thefrequency and the number of the gate lines. As the gate on timedecreases, a data signal is not sufficiently applied to the pixel. Thiscauses a charging rate within the pixel electrode to be decreased andquality of the display apparatus to be deteriorated.

SUMMARY OF THE INVENTION

Accordingly, it is an aspect of the present invention to provide an LCDimproving a charging rate of the pixel electrode by increasing a gate ontime and a driving method of the same.

The foregoing and/or other aspects of the present invention are alsoachieved by providing an LCD comprising a plurality of data linesextending in a first direction, a plurality of gate lines extending in asecond direction defining with the plurality of data lines a pluralitypixel areas arranged in a matrix configuration and supplying a gatesignal to at least two rows of the pixel areas simultaneously, and thinfilm transistors connected with the plurality of gate lines and theplurality of data lines.

According to the present invention, the number of the data linesdisposed between the adjacent pixel areas in a row direction is the sameas that of the rows of the pixel area supplied with the same gatesignal.

According to the present invention, a plurality of the gate lines applya common gate signal to the pixel areas in a row direction.

According to the embodiment of the present invention, the number of therows of the pixel areas supplied with the common gate signal is two.

According to the embodiment of the present invention, the adjacent pixelareas in a column direction are connected to data lines having oppositepolarities.

According to the embodiment of the present invention, one of theadjacent rows of the pixel area in the column direction is connected toan odd-numbered data line, and the other is connected to aneven-numbered data line.

According to the embodiment of the present invention, one of theadjacent pixel areas in a row direction is connected to an odd-numbereddata line, and the other is connected to an even-numbered data line.

According to the embodiment of the present invention, the LCD furthercomprising a data driver supplying the data line with a data signal anda controller controlling the data driver, wherein the controllercontrols the data driver to supply the same polarity of data signals tothe data lines disposed between the pixel areas.

According to the embodiment of the present invention, the LCD furthercomprising a data driver supplying the data line with a data signal anda controller controlling the data driver, wherein the controllercontrols the data driver to supply the different polarity of datasignals to the data lines disposed between the pixel areas.

According to the embodiment of the present invention, the LCD furthercomprising an backlight unit providing light of three primary colors tothe pixel area sequentially by one frame period.

According to the embodiment of the present invention, a frequency offrame is higher than 180 Hz.

The foregoing and/or other aspects of the present invention are alsoachieved by providing a driving method for an LCD comprising a TFTsubstrate on which pixel areas are arranged in a matrix layout formed bya gate line and a data line crossing the gate line and a backlight unitproviding the TFT substrate with light of three primary colors. Themethod comprises providing the TFT substrate with light of the threeprimary colors sequentially in one frame period and supplying at leasttwo rows of pixel areas with a gate signal simultaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects and advantages of the present inventionwill become apparent and more readily appreciated from the followingdescription of the exemplary embodiments, taken in conjunction with theaccompanying drawings of which:

FIG. 1 is a view of an LCD according to a first embodiment of thepresent invention;

FIG. 2 is an arrangement view of a TFT substrate illustrating a drivingmethod for the LCD according to the first embodiment of the presentinvention;

FIG. 3 is an arrangement view of a TFT substrate illustrating a drivingmethod for an LCD according to a second embodiment of the presentinvention; and

FIG. 4 is an arrangement view of a TFT substrate illustrating a drivingmethod for an LCD according to a third embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout.

First Embodiment

The first embodiment of the present invention will be appreciated byreference to FIGS. 1 and 2.

As shown in FIG. 1, an LCD comprises a TFT substrate 100 and anbacklight unit 200.

The TFT substrate 100 comprises data lines 120, 120 a and 120 b; andgate lines 110 a and 110 b crossing the data lines 120 a, 120 b and 120thereby forming a pixel area 140 arranged in a matrix array; and a TFT130 disposed at an intersection of the gate line 110 a and the data line120.

Here, a pair of the gate lines 110 a and 110 b are connected with eachother at their ends. Therefore, a single gate signal supplied by a gatedriver (not shown) is applied to the pair of gate lines 110 a and 110 bat the same time. With this configuration, two rows of the pixel area140 are driven for one gate on time.

In a conventional LCD, the gate signal supplied by a gate driver isapplied to only one gate line at a time, thereby driving only one row ofthe pixel area 140. Unlike the conventional driving method, in a fieldsequential color (hereinafter referred to as ‘FSC’) driving method, red,green and blue lights are sequentially radiated for forming one frame.In other words, the number of the gate signals applied to the gate linehas to be three times as much as a frequency recognized by a user toform one frame in the FSC driving. For example, the actual frequency forthe FSC driving has to be higher than 180 Hz so that the user considersthe image to be 60Hz. Accordingly, the gate on time for a displayapparatus having a 1280*1024 resolution and an apparent frequency of 60Hz equals 1/(the apparent frequency*the number of the gate lines*3),i.e. 1/(60*1024*3)=5.425 μs.

However, when a gate signal is applied simultaneously to the pair ofgate lines 110 connected with each other, the gate on time becomes10.850 μs which is twice as long as the conventional gate on time. Asthe gate on time increases, a time for charging data signals in thepixel area 140 is also prolonged, thereby improving a charging rate inthe pixel electrode. Further, since passages connecting the gate driversand the gate lines are halved, the number of the gate pads and the gatedrivers is also halved.

Although two gate lines 110 are connected at their ends in the firstembodiment, more than three gate lines may be connected with oneanother. Since the display apparatus adopting an impulsive driving,producing a black image between the frames, should be driven twice asfast as the conventional display apparatus, the impulsive drivingdisplay apparatus can also employ the above configuration of the presentinvention that applies one gate signal to the multiple gate linessimultaneously.

The data line 120 crosses the gate line 110, thereby forming the pixelarea 140 arranged in the matrix array. The data line 120 is arranged insuch a way that two data lines 120 a and 120 b are disposed at oppositesides of one pixel area 140. In other words, the two data lines 120 aand 120 b are disposed between the adjacent pixel areas 140. Since thesame gate signal is applied to two rows of the pixel area 140, the abovearrangement for the data lines 120 a and 120 b is required to applydifferent data signals to the adjacent pixel areas 140 in a columndirection. The TFTs 130 are appropriately arranged at intersections ofthe two gate lines 110 a and 110 b and the two data lines 120 a and 120b so that the same data signal is not applied to the adjacent pixelareas 140 in a column direction. As shown in FIG. 1, one of the adjacentpixel rows is connected to the odd-numbered data line 120 a, and theother is connected to the even-numbered data line 120 b.

The number of the data lines 120 disposed between the pixel areas 140corresponds to the number of rows of the pixel area 140 where the samegate signal is applied, i.e. the number of the gate lines 110 connectedwith one another at their ends. Therefore, the number of the gate lines110 connected with one another is proportional to the number of the datalines 120 disposed between the pixel areas 140. As described before,more than three gate lines 110 may be connected with one another. Inthis case, more than three data lines 120 are disposed between theadjacent pixel areas 140 arrayed in a row direction. Since color filtersare not used in the FSC driving, one pixel area 140 is three timeslarger than that of the conventional LCD. Accordingly, disposing threedata lines 120 between the pixel areas 140 does not make a bigdifference in an aperture ratio.

The TFT 130 delivers the gate signal supplied from the gate line 110 andthe data signal supplied from the data line 120 to the pixel area 140.As shown in FIG. 1, the adjacent TFTs 130 arrayed in a column directionare connected to different data lines 120 a and 120 b, thereby beingarranged in a zigzag form. Such arrangement of the TFTs 130 allows theadjacent pixel areas 140 arrayed in a column direction to be connectedto different data lines 120 a and 120 b, respectively. Accordingly, theadjacent pixel areas 140 arrayed in a column direction are supplied witha different data signal.

The backlight unit 200 comprises a plurality of LEDs 210 (light emittingdiode) and a supporter (not shown) supporting the LED 210, a diffusingplate (not shown) diffusing the light from the LED 210 and a LEDsubstrate. Each LED 210, is a point light source, emits red, green andblue lights.

The backlight unit 200 may be a direct type providing light from belowthe TFT substrate 100 or an edge type providing light from a side of theTFT substrate 100.

A driving method for an LCD according to the first embodiment of thepresent invention will be described with reference to FIG. 2. As shownin FIG. 2, the TFT substrate 100 comprises not only the gate line 110and the data line 120 but also a gate driver 150, a data driver 160 anda controller 170.

The gate driver 150 supplies the gate line 110 with a number of controlsignals driving the gate line 110. The gate driver 150, synchronizedwith a starting signal (STV) and a gate clock (CPV) from the controller170, supplies each gate line 110 with the gate on voltage.

The data driver 160 converts an image data signal, synchronizing withclock (HCLK), into a corresponding gray scale voltage, and then deliversappropriate data signals to each data line 120 according to a loadsignal from the controller 170.

The LCD adopts an inversion driving method inverting a polarity of thedata signal supplied to the pixel area 140 by frame. Generally, a frameinversion or a line inversion causes a flicker, therefore a dotinversion is widely adopted. While the frame inversion inverts thepolarity of the data signal by frame, the line inversion inverts by gateline. In the dot inversion, the adjacent pixels have differentpolarities.

As shown in FIG. 2, the data driver 160 inverts the polarity of the datasignal by data line 120. The two data lines 120 a and 120 b disposedbetween the adjacent pixel areas 140 arrayed in a row direction aresupplied with the data signals having the same polarity. Meanwhile, theadjacent pixel areas 140 arrayed in a column direction are connected todifferent data lines 120, therefore, they are supplied with the datasignals having different polarities. Though the data driver 160 suppliesthe data signals having different polarities by line, the result is thesame as in the dot inversion. With this configuration, the flicker canbe cleared.

The controller 170 produces a number of the control signals driving thegate line 110 and the data line 120, and controls the data driver 160 tosupply the data signals having different polarities by data line 120.The dot inversion depends on how the pixel area 140 and the data line120 are connected and what polarity of the data signal is applied to thedata line 120, therefore the dot inversion can be embodied by variouscombinations of them. After a wiring pattern of the TFT substrate 100 iscompleted by connecting the pixel area 140 and the data line 120, thecontroller 150 controls the data driver 140 to produce the data signalshaving different polarities, thereby carrying out the dot inversion.

Second Embodiment

A second embodiment of a driving method of an LCD according to thepresent invention will be appreciated in by referring to FIG. 3 inconnection with the following explanation.

The elements of the second embodiment that are identical to the elementsof the first embodiment have the same reference numerals as the elementsof the first embodiment. Moreover, the descriptions of the elements ofthe second embodiment that are identical to the elements of the firstembodiment have been omitted for the sake of brevity. Data drive 160-1differs from data drive 160 only in the order of the polarity of theoutput signals on the data lines.

As shown in FIG. 3, pixel areas 140 in a column direction are connectedalternatively to the pair of data lines for data lines associated withthe column of pixel areas. Adjacent columns of pixel areas 140 aresymmetric with respect to the data line disposed therebetween. One ofthe adjacent pixel areas 140 in a row direction is connected to anodd-numbered data line (120 a), and the other is connected to aneven-numbered data line (120 b).

For performing the dot inversion, a positive polarity (+) of data signalis applied to the odd-numbered data line 120 a, and a negative polarity(−) of data signal is applied to the even-numbered data line 120 b. Orstated differently, that means opposite polarity data signals areapplied to adjacent data lines alternatively. Like the above, the dotinversion can be performed by adjusting an arrangement of the pixelareas 140 and the polarity of the data signal.

Third Embodiment

Referring to FIG. 4, a driving method for an LCD according to a thirdembodiment of the present invention will be described. As shown in FIG.4, gate lines 110 c and 110 d drive in common adjacent rows of pixels.For example, gate line 110 c drives two rows of pixel areas 140 a and140 b. Similarly, gate line 110 d supplies a common gate signal to tworows of pixel areas 140 c and 140 d. Viewed in the column direction, theadjacent pixel areas 140 a through 140 d viewed from a data drivestandpoint are electrically separated. Thus the adjacent pixel areas 140in a column direction are supplied with different polarity data signals.Since gate line 110 c drives the two rows of pixel area 140 a and 140 b,every TFT 130 belonging to the two rows of pixel areas 140 a and 140 bis connected to gate line 110 c, and is connected to different rows ofpixel areas 140 alternatively along the row direction. Controller 170controls a data driver 160 so that adjacent pixel areas 140 viewed inthe column direction are provided with different polarity of the datasignals. Accordingly, like the layout in FIG. 2, the data driver 160supplies different polarity data signals to the two adjacent data line120 a and 120 b in a row direction disposed between the adjacent pixelareas 140.

In case that the TFTs 130 of FIG. 4 are arranged in the same way as inFIG. 3, the data signals having different polarity are appliedalternatively to the data lines 120 and at the same time the polarity ofthe data signal is inverted by gate line 110 for the dot inversion.

Although only a few embodiments of the present invention have been shownand described, it will be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe appended claims and their equivalents.

1. A liquid crystal display (LCD) comprising: a plurality of data linesextending in a first direction; a plurality of gate lines extending in asecond direction defining with the plurality of data lines a pluralitypixel areas arranged in a matrix configuration and supplying a gatesignal to at least two rows of the pixel areas simultaneously; and thinfilm transistors connected with the plurality of gate lines and theplurality of data lines.